Continuous extrusion apparatus

ABSTRACT

Continuous extrusion apparatus having a rotating circumferential groove (72) carrying feedstock to a passageway formed between the groove and arcuate tooling extending into the groove has the groove formed on the central region (72) of a cylinder (2). The cylinder (2) is formed with end bosses (16, 18) which are supported in bearings (4) such that deflection arising from generating very high extrusion pressures in the passageway is minimised and stresses are distributed to the bearings (4) in a manner avoiding concentrations or the incidence of unacceptably high variations in local stress levels. The cylinder (2) is end connected to a drive shaft (24) outboard of the bearing (4) with a splined end portion (22) of the drive shaft locating in an end recess (20) in the cylinder (2). Alternatively a bolted connection may be used. A tie bolt (36) extends coaxially of the cylinder (2) and serves to apply a compressive axial loading to the cylinder to counter tension stresses arising during extrusion. The bearings (4) include rollers (48) directly in contact with the end bosses (16, 18) of the cylinder, the cylinder being free to expand axially relative to one set of rollers (48). Cooling and lubricating fluid is supplied to the bearings (4) and end bosses (16, 18). Coolant may also be directed through passages lined with copper sleeves extending axially of the cylinder (2). The bearing surfaces on the bosses (16, 18) and the central region (70) of the cylinder (2) are formed as regions of increased hardness relative to the remainder of the cylinder.

This invention relates to apparatus for the forming of metals by acontinuous extrusion process in which feedstock is introduced into arotating circumferential groove to pass into a passageway formed betweenthe groove and arcuate tooling extending into the groove.

In EP-A-0 071 490 there is described continuous extrusion apparatusutilising circumferentially grooved means rotatably mounted on a bed.

According to the present invention, there is provided a continuousextrusion apparatus utilising circumferentially grooved means rotatablymounted on a bed, wherein the circumferentially grooved means comprisesa circumferentially grooved cylinder carried on bearings on the bed andend coupled to a drive shaft.

In order to exploit fully the continuous extrusion forming process, veryhigh extrusion pressures are utilised such that very high levels ofstress are generated. Hitherto to operate the process acircumferentially grooved wheel mounted on a drive shaft running inassociated bearings has been utilised. However, the wheel tends to orbitrelative to the shaft and to deform which may lead either to damage orearly failure of the wheel assembly or leakage of feedstock material andloss of extrusion pressure due to deflection of the wheel assembly underload, or both. Where the wheel is keyed or splined to the shaft, theorbiting effect may lead to fretting at the keys or splines, againleading to possible early failure.

The invention will now be described, by way of example, with referenceto the accompanying, partly diagrammatic, partially axiallycross-sectioned, portion of a continuous extrusion apparatus.

As shown, a circumferentially grooved cylinder 2 is mounted in bearings4 positioned in bushes 6 carried in a frame 8 positioned on a bed 10.The cylinder is formed with a central, circumferentially grooved,portion 12 flanked by a pair of circumferential flanges 14 and a pair ofouter, end, bosses 16, 18. One end boss 16 is formed with a splinedrecess 20 arranged to co-act with a correspondingly splined end portion22 of a coupling shaft 24. A retaining ring 26 bears against a shoulder28 on the coupling shaft to retain the splined end portion 22 in thesplined recess 20. The other end portion 30 of the coupling shaft issplined into an output drive 32 of a gear box 34 connected to anelectric motor (not shown). In an alternative arrangement (not shown)the coupling shaft is bolted to an end face of the circumferentiallygrooved cylinder 2.

As shown, a pre-loading tie bolt 36 is positioned centrally of a bore 38in the cylinder 2 from a base portion 40 of the splined recess 20 to theend boss 18 and is provided with a nut 42 co-acting with a threadedportion 44 of the tie bolt. Compressive stress is induced in thecylinder by tightening the nut 42 on the tie bolt 36 against an end face46 of the boss 18, in order that, when the apparatus is in operation anda radial loading is applied through arcuate tooling urged into contactwith the cylinder 2 over a short arc, the resultant stress loading inthe cylinder 2 is nontheless maintained as compressive around the fullcircumference. However, it is envisaged that, in some instances, it willnot be necessary to apply such a compressive pre-stressing and thatfabricating the cylinder 2 as a solid integer will provide asufficiently rigid arrangement. Whilst the fatigue life of the solidcylinder may be less than the fatigue life of a pre-loaded wheel mountedon a shaft, this is not considered to be disadvantageous overall sinceall the material subject to high stress levels is replaced when itbecomes necessary to replace a wheel and the reduced fatigue life of thepresent arrangement is likely to be greater than the wear out life of awheel arrangement.

The bearings 4 include a multiplicity of rollers 48 running in aradially outer raceway 50 mounted on the bushes 6. The rollers 48 rundirectly on the faces 52 on the cylinder 2, with the cylinder beinglocated axially by positioning the rollers at the boss 16 between ashoulder 54 on the cylinder 2 and a flanged ring 56 held in position bythe retaining ring 26. To accommodate axial thermal expansion, the boss18 is free to move axially of the rollers 48.

Each bush 6 is formed with an inlet duct 58 for the supply oflubricating and cooling fluid to the bearing 4. The inlet duct 58discharges to a circumferential chamber 60 formed between the bush 6 andthe respective end boss 16, 18 and flexible end seal means 62, 64. Anoutlet duct 68 extends from the chamber 60 through the bush 6. In orderto extract heat from the bosses 16, 18 and to lubricate the rollers 48,a fluid, such as an oil or a water based emulsion, is circulated throughthe inlet ducts 58 to the circumferential chambers 60 and discharged toa cooler means (not shown) through the outlet ducts 68.

In an alternative arrangement (not shown) coolant is directed to flowover the surface of end regions of the cylinder 2 and a separate flow oflubricant is directed to the bearings 4.

In another alternative arrangement (not shown) interconnected axialpassages are drilled in the cylinder 2, adjacent the cylindricalsurface, and are channelled to a co-axial distributor and collectormeans adjacent the boss 18. The axial bores may be lined with, forexample, expanded copper sleeves to reduce thermal shock and increaseheat extraction rates.

The central portion 12, as shown, is formed with a pair of grooves 70,which, if desired, are positioned in a region 72 of increased hardnessas compared with the hardness of the remainder of the cylinder 2. Theregion of increased hardness may be achieved, or subsequently reclaimed,for example, by forming the solid cylinder with an insert of hardermaterial, by utilising an induction heating and hardening process, bylaying down a weld deposit of harder material, by metal spraying, bynitriding, by diffusion techniques or by ion implantation. Regions ofthe end bosses 16, 18 in registration with the rollers 48 may behardened in a similar manner. It will be appreciated that but a singlecircumferential groove may be provided or, alternatively, severalcircumferential grooves may be provided.

By virtue of the coupling between the solid cylinder 2 and the outputdrive shaft 32 of the gear box 34 being located outboard of the centerof the bearing 4, torque is transmitted through a connection not subjectto radial loading, thereby avoiding drawbacks inherent in the previousarrangements, Since the cylinder carries the circumferential groovingdirectly, the radial loading is transmitted directly to the supportbearings thereby achieving a highly rigid assembly which is not subjectto orbiting.

I claim:
 1. A continuous extrusion apparatus having a circumferentiallygrooved member rotatably mounted on a bed, said circumferentiallygrooved member comprises:a) circumferentially grooved cylinder havingfirst and second ends, said circumferentially grooved cylinder carriedon bearings for rotational movement on said bed and end coupled at oneof said first and second ends to a drive shaft, said end coupling isoutboard of said bearings.
 2. A continuous extrusion apparatus asclaimed in claim 1, and wherein said circumferentially grooved cylinderis formed as a solid integer.
 3. A continuous extrusion apparatus asclaimed in claim 1, and wherein said circumferentially grooved cylinderis formed with a central, axially extending, through bore, a tie bolt islocated in said through bore and provided with a nut arranged to apply acompressive axial loading to said circumferentially grooved cylinder. 4.A continuous extrusion apparatus as claimed in claim 1, and wherein saidfirst and second ends of said circumferentially grooved cylinder isformed with a splined recess arranged to coact with a splined endportion of said drive shaft.
 5. A continuous extrusion apparatus asclaimed in claim 1, and wherein said bearings include rollers arrangedto run in tracks mounted in bushes positioned on said bed and to run incontact with end bosses formed on said circumferentially groovedcylinder.
 6. A continuous extrusion apparatus as claimed in claim 5, andwherein axial movement of said circumferentially grooved cylinderrelative to said rollers is constrained at one of said end bosses withthe other of said end bosses being free to move axially relative to therespective one of said rollers to accommodate axial thermal expansion ofsaid circumferentially grooved cylinder.
 7. A continuous extrusionapparatus as claimed in claim 1, and further including means forsupplying a cooling fluid to flow over end region surfaces of saidcylinder.
 8. A continuous extrusion apparatus as claimed in claim 1, andfurther including means for supplying a cooling and lubricating fluid tosaid bearings to flow in contact with said end portions of saidcircumferentially grooved cylinder.
 9. A continuous extrusion apparatusas claimed in claim 1, and further including axially extending passagesfor the flow of cooling fluid formed in said circumferentially groovedcylinder and connected to a co-axial connector at one end of saidcylinder.
 10. A continuous extrusion apparatus as claimed in claim 9,and further including sleeves of a metal of relatively high thermalconductivity expanded into contact with wall portions of said passagesfor flow of cooling fluid.
 11. A continuous extrusion apparatus asclaimed in claim 1, and wherein at least a portion of the groovingformed within said circumferentially grooved cylinder is of a materialhaving a hardness greater than about the hardness of the remainingportion of said cylinder.
 12. A continuous extrusion apparatuscomprising:a) a base; b) a circumferentially grooved cylinder havingfirst and second ends; c) bearings for rotatably mounting saidcircumferentially grooved cylinder to said base, said bearings providedat each of said first and second cylinder ends; and d) a drive shaft forconnection to said circumferentially grooved cylinder at one of saidfirst and second ends, said connection is outboard of said bearings. 13.A continuous extrusion apparatus comprising:a) a support bed; b) acircumferentially grooved forming member having first and second ends;c) means for rotatably mounting said circumferentially grooved formingmember to said bed, said mounting means provided at each of said firstand second ends; d) means for rotating said circumferentially groovedforming member; and e) means for connecting said rotating means to oneof said circumferentially grooved forming member first and second ends,said connecting means is outboard of said mounting means.